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Title:Expansive Characteristics of Reclaimed Asphalt Pavement (RAP) Used As Base Materials
Author(s):Deniz, Derya; Tutumluer, Erol; Popovics, John S.
Subject(s):reclaimed asphalt pavement (RAP)
Abstract:Reclaimed asphalt pavement (RAP) is the reprocessed hot-mix asphalt (HMA) pavement material containing asphalt and aggregates. A viable solution for deposing of large quantities of RAP is to incorporate them into base and subbase applications for highway construction. However, RAP materials may contain an expansive aggregate, such as steel slag, that is not allowed in pavement substructure layers in Illinois. Steel slag aggregates are particularly useful in areas where high frictional properties are required, such as HMA surface courses, yet, they may contain free lime and magnesia that may cause the slag to expand when reacted with water. The overall objective of this research project was to determine the expansive properties for RAP materials, especially the materials including recycled steel slag aggregates, with respect to those of the virgin aggregates, and evaluate their potential use as pavement base materials in Illinois. Seventeen RAP materials and virgin aggregates were tested for their expansive characteristics in the laboratory following the ASTM D4792 “Potential Expansion of Aggregates from Hydration Reactions” test method. The specimens in California Bearing Ratio (CBR) test molds were submerged into a high alkali cement water solution (pH of 12) and kept constantly soaked at 70°C to accelerate hydration reactions. The expansion percentage of the CBR specimens and the temperature and pH levels of the solution were measured continuously on a daily basis during the soaking period for a minimum of 7 days and maximum 60 days until the expansion curve flattened or the expansion rate slowed down. Some steel slag aggregates showed considerably high expansion potentials, up to 6.2% swell, due to the hydration of free lime when compared to other virgin aggregates, such as siliceous gravel and crushed dolomite, which had minor or almost no expansion. The RAP materials, which often had lower densities, exhibited more of an initial settlement or contraction before any kind of expansion with time. Two RAP materials, surface RAP with 92% steel slag aggregates and steel slag RAP, gave the maximum expansion amounts 1.69% and 1.46%, respectively. When compared to the high expansion potentials of especially the virgin steel slag aggregates, the RAP materials had much lower tendencies to expand most likely due to an effective asphalt coating around the aggregate which prevents any significant ingress of water into the aggregate.
Issue Date:2009-08
Series/Report:ICT-09-055 UILU-ENG-2009-2036
Genre:Technical Report
Publication Status:published or submitted for publication
Peer Reviewed:not peer reviewed
Sponsor:Illinois Department of Transportation
Rights Information:No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161
Date Available in IDEALS:2013-11-07

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